Neural - Ventricular System Development

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Human- ventricular system cartoon.jpg

Introduction

The ventricular system develops from the single cavity formed from the hollow neural tube. This fluid-filled space is separated from the amnion following fusion of the neural tube and closure of neuropores. At different regions sites within the wall (floor of lateral ventricle and roof of the third and fourth ventricles) differentiate to form choroid plexus a modified vascular structure which will produce Cerebrospinal fluid (CSF)

Human choroid plexus (stage 22)

In development and the space within the spinal cord (central canal) and the brain (ventricles) was derived from the same space within the neural tube. In the adult these 2 spaces remain connected containing the same CSF.

Early in development the cavity within the neural tube (which will form the ventricular space) is filled with amniotic fluid. As the brain and spinal cord grow, this fluid filled space makes up the majority of the nervous system (by volume). Upon closure of the neuropores and development of the embryonic vasculature, this fluid is then synthesized by the choroid plexus, a specialized vascular epithelium. In mammals, the choroid plexuses develop at four sites in the roof of the neural tube shortly after its closure, in the order fourth (IV), lateral, and third (III) ventricles.

The choroid plexuses form one region of the blood-brain barrier that regulates the brain's internal environment.

Normal CSF contains high amounts of salts, sugars and lipids and low amounts of protein (0.3-0.7 microg/microL), though there appears to be 60+ proteins as identified by 2D gel. Presence of some protein in the CSF can be indicative of disruption of or incomplete blood/brain barrier.


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Some Recent Findings

  • 4D fluorescent imaging of embryonic quail development[1] "Traditionally, our understanding of developmental biology has been based on the fixation and study of embryonic samples. Detailed microscopic scrutiny of static specimens at varying ages allowed for anatomical assessment of tissue development. The advent of confocal and two-photon excitation (2PE) microscopy enables researchers to acquire volumetric images in three dimensions (x, y, and z) plus time (t). Here, we present techniques for acquisition and analysis of three-dimensional (3D) time-lapse data. Both confocal microscopy and 2PE microscopy techniques are used. Data processing for tiled image stitching and time-lapse analysis is also discussed. The development of a transgenic Japanese quail system, as discussed here, has provided an embryonic model that is more easily accessible than mammalian models and more efficient to breed than the classic avian model, the chicken."

Development Overview

The initial neural grove and tube, with open neuropores, is filled with amniotic fluid. By stage 13 (4 weeks, GA week 6) the neuropores are closed and the neural tube is no longer directly connected to the amniotic cavity. Initially during early 3 and 5 vesicle neural stages and prior to choroid plexus development, the "ventricular space" is reliant upon overall tube growth and directional fluid transport to maintain the fluid-filled space. There is research suggesting that hydrostatic pressure[2] and a functioning heart are required to maintain the vesicle spaces, and there are several models as to how pressure and osmotic gradients may be established. See also zebrafish model studies[3] and a recent review.[4]

Ventricles and Central Canal

Human Embryo (week 8, Stage 22) ventricular system
Human Fetus (week 10) showing choroid plexus and early ventricular system

Stage 11 - appearance of the optic ventricle. The neural groove/tube space is initially filled with amniotic fluid.

Stage 12 - closure of the caudal neuropore, onset of the ventricular system and separates the ependymal from the amniotic fluid

Stage 13 - cavity of the telencephalon medium is visible

Stage 14 - cerebral hemispheres and lateral ventricles begin, rhomboid fossa becomes apparent.

Stage 15 - medial and lateral ventricular eminences cause indentations in the lateral ventricle

Stage 16 - hypothalamic sulcus is evident

Stages 17-18 - interventricular foramina are becoming relatively smaller, and cellular accumulations indicate the future choroid villi of the fourth and lateral ventricles

Stage 18 - areae membranaceae rostralis and caudalis are visible in the roof of the fourth ventricle, and the paraphysis is appearing.

Stage 19 - choroid villi are visible in the fourth ventricle, and a mesencephalic evagination (blindsack) is visible

Stage 20 - choroid villi are visible in the lateral ventricle

Stage 21 - olfactory ventricle is visible

Stages 21-23 - lateral ventricle has become C-shaped (anterior and inferior horns visible). Recesses develop in the third ventricle (optic, infundibular, pineal).

(Data from O'Rahilly R, Müller F., 1990[5])

Fetal

Fetal Period - posterior horn of the lateral ventricle, choroid plexus of the third ventricle, suprapineal recess, interthalamic adhesion, aqueduct, and apertures in the roof of the fourth ventricle.

Brain ventricles and ganglia development 03.jpg

Choroid Plexus Development

In humans, the choroid plexuses develop at four sites in the roof of the neural tube shortly after its closure, in the order fourth (IV), lateral, and third (III) ventricles.

Human- ventricular system cartoon.jpg Human Ventricular System

A schematic diagram of structures and specialized cell types bordering the different parts of the mammalian ventricular system, and in contact with the cerebrospinal fluid (CSF)[6]

Abbreviations:

  • CO - caudal opening of the central canal of the spinal cord
  • H - hypothalamic CSF-contacting neurons
  • HY - Hypophysis
  • LV - lateral ventricle
  • ME - median eminence
  • O - vascular organ of the terminal lamina
  • PIN - pineal organ
  • R - raphe nuclei
  • RET - retina
  • RF - Reissner's fiber
  • SE - septal region
  • SCO - subcommissural organ
  • SP - medullo-spinal CSF-contacting neurons
  • TEL - telencephalon
  • TF - terminal filum

Epithelium from the neural tube epithelium.

Mesenchyma from the meninges.

Enzymes required for CSF production are Na+/K+ ATPase and carbonic anhydrase.

Subarachnoid Space Development

  • Stage 14 (33 days) - initially as irregular spaces on the ventral surface of the spinal cord.
  • Stage 18 (44 days) - dura mater is formed and spaces surround the circumference of the spinal cord, which coalesce and contain many blood vessels.

Data from Patelska-Banaszewska M, Wozniak W. (2005)[7]

CSF Synthesis

Two key enzymes are required to produce CSF they are the Na+/K+ ATPase and carbonic anhydrase.

Other known chorid plexus enzymes include: alkaline and acid phosphatases, magnesium-dependent ATPase, glucose-6-phosphatase, thiamine pyrophosphatase, adenylate cyclase, oxidoreductase, esterases, hydrolases, cathepsin D, and glutathion S-transferase. (More? Catala M., 1998)

"The epithelial cells of the choroid plexus secrete cerebrospinal fluid (CSF), by a process that involves the movement of Na(+), Cl(-) and HCO(3)(-) from the blood to the ventricles of the brain. This creates the osmotic gradient, which drives the secretion of H(2)O. The unidirectional movement of the ions is achieved due to the polarity of the epithelium, i.e., the ion transport proteins in the blood-facing (basolateral) are different to those in the ventricular (apical) membranes."[8]

CSF Reabsorption

Arachnoid Granulation (image: Gray's Anatomy)

CSF drainage (absorption or reabsorption) into the venous system is through arachnoid granulations.

CSF in the subarachnoid space extends into the arachnoid granulations, which then project through the dura into the superior sagittal sinus.

See also note in CSF Circulation section, point 3.

Adult CSF Normal Values

CNS ventricles

Lumbar CSF

  • Opening pressure: 50–200 mm H2O CSF
  • Color: Colorless
  • Turbidity: Crystal clear
  • Mononuclear cells: less than 5 / mm3
  • Polymorphonuclear leukocytes: 0
  • Total protein: 22–38 mg/dl Range 9–58 mg/dl (mean ± 2.0 SD)
  • Glucose: 60–80% of blood glucose

(Data from: Clinical Methods, 3rd ed, Table 74.1)

CSF Circulation

Ventricular space cartoon

Information below is for the adult and is based upon data from a radiologic investigation using MR imaging and radionuclide cisternography.[9]

  1. CSF-circulation is propelled by a pulsating flow, which causes an effective mixing. Flow is produced by the alternating pressure gradient, which is a consequence of the systolic expansion of the intracranial arteries causing expulsion of CSF into the compliant and contractable spinal subarachnoid space.
  2. No bulk flow is necessary to explain the transport of tracers in the subarachnoid space.
  3. Main absorption of the CSF is not through the Pacchionian granulations (arachnoid granulations), but a major part of the CSF transportation to the blood-stream is likely to occur via the paravascular and extracellular spaces of the central nervous system. (MH- Note this statement conflicts with previous CSF Reabsorption in literature)
  4. The intracranial dynamics may be regarded as the result of an interplay between the demands for space by the four components of the intracranial content (arterial blood, brain volume, venous blood and CSF).
  5. Interaction has a time offset within the cerebral hemispheres in a fronto-occipital direction during the cardiac cycle (the fronto-occipital "volume wave").
  6. Outflow from the cranial cavity to the cervical subarachnoid space (SAS) is dependent in size and timing on the intracranial arterial expansion during systole.

References

  1. <pubmed>22046043</pubmed>
  2. <pubmed>15977221</pubmed>
  3. <pubmed>9007238</pubmed>
  4. <pubmed>19154733</pubmed>
  5. <pubmed>2285038</pubmed>
  6. <pubmed>20157443</pubmed>| Cerebrospinal Fluid Res.
  7. <pubmed>16228957</pubmed>
  8. Mechanisms of CSF secretion by the choroid plexus. Speake T, Whitwell C, Kajita H, Majid A, Brown PD. Microsc Res Tech. 2001 Jan 1;52(1):49-59. Review. PMID: 11135448
  9. <pubmed>8517189</pubmed>

Journals

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Reviews

<pubmed></pubmed> <pubmed></pubmed> <pubmed>19154733</pubmed> <pubmed>18293362</pubmed> <pubmed>11135444</pubmed> <pubmed>9754371</pubmed>

Articles

<pubmed></pubmed> <pubmed></pubmed> <pubmed>15478101</pubmed> <pubmed>2210106</pubmed> <pubmed>3813041</pubmed> <pubmed>7351160</pubmed> <pubmed>909616</pubmed>


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Cite this page: Hill, M.A. (2024, March 28) Embryology Neural - Ventricular System Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Neural_-_Ventricular_System_Development

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